The attack on Monday came a day after a brief US-brokered local ceasefire expired and less than a week before the United States is due to bring together Ukrainian and Russian delegations in Abu Dhabi for talks on ending the war, now in its fifth year.
Reuters footage on Wednesday showed men in military fatigues loading bodies in white plastic bags into the back of a van in the village of Komyshuvakha, which was struck multiple times.
Excavators were digging up earth near a huge blast crater while rescue workers searched underground for bodies.
Ukrainian President Volodymyr Zelenskiy has said Russian forces first dropped aerial bombs on an underground school building being used as a distribution point as people arrived to collect aid, then struck the shelter with more bombs.
Two members of a rescue crew and four police officers were among the dead, emergency services said.
Russia's Defence Ministry said the attack targeted Ukrainian military units around Komyshuvakha and two other settlements, and that up to 25 Ukrainian servicemen were killed.
Russia and Ukraine both deny deliberately targeting civilians.
In a social media post, the national police said several strikes hit the area, including from a three-ton FAB bomb, which is a large bomb fitted with a glide kit that allows it to fly long distances after being dropped from a Russian warplane.
According to defence intelligence websites, a three-ton glide bomb would carry around 1.4 tons of explosives.
The strike occurred a day after a six-day ceasefire to evacuate civilians from the Russian-occupied southern Ukrainian town of Oleshky expired.
The truce, brokered by US first lady Melania Trump, allowed nearly 800 people to be evacuated, according to the first lady. Zelenskiy awarded Melania Trump a state honour for her role.
The US will bring together delegations from Ukraine and Russia in Abu Dhabi on Monday and Tuesday to discuss ending the conflict, postwar security agreements and de-escalation.
